In industries and commercial buildings where heat is removed by heat exchangers, chillers or the like, the warm water is cycled through a cooling tower to be cooled and then re-circulated. Because of evaporation, the dissolved solids in the water become concentrated.
The sparingly soluble salts like calcium carbonate and magnesium carbonate may begin to deposit on pipes, similarly algae and/or microorganisms may multiply, clogging up the passage and heat exchanger tubes and reducing the heat transfer efficiency.
In an attempt to maintain the heat transfer efficiency, chemicals such as biocides, anti-scalant and anti-corrosion have been traditionally used. This will require disposal of large volumes of water containing toxic chemicals.
With the increasing ecological and environmental awareness and safety concerns, alternative and sustainable methods are now emphasized and sought after.
A recent method of limiting scale deposition and microorganism multiplication are achieved by electrolysis, wherein a pair of electrodes is used for depositing mineral contents contained in the cooling water as precipitated scale and dislodging such scale by electrode polarity reversal at a predetermined time interval, thereby limiting the buildup of scale. In addition, chlorine produced in the electrolytic process has a sterilization effect in the cooling water, thus enabling control of algae and/or microorganism multiplication. In this way, the attachment of scale and microorganisms can be limited without using any chemical and the cycle of concentration can be increased to lower water wastage.
However, where the conductivity of the cooling water exceeds a threshold value, the device for conducting the electrolytic process is unable to work, for example in a situation like an abrupt increase in the hardness of the cooling water caused by the intense evaporation of the water. In order to deal with this problem, the whole system has to be stopped and the entire cooling water has to be changed. This will cause excessive water wastage and disruption of the system that will result in greater energy wastage due to restarting of the system. In addition, due to the fact that the conductivity cannot be controlled, the water may be over or under electrolyzed. Over electrolyzing may cause pipe leakage due to corrosion. High amperage can reduce the life span of the electrodes and cause unnecessary waste of electricity. On the other hand, under electrolyzing may degrade descaling performance.
An object of the present invention is to ameliorate at least one of the above-mentioned problems.